Sewing machine



Feb. 25, 1936'.

C. W. SCHWEIGER SEWING MACHINE Filed April 4, 1934 Patented Feb. 25,1936 UNITED STATES PATENT OFFICE Application April 4,

1934, Serial No. 718,907

.In Germany May 4, 1933 2 Claims.

This invention relates to a drive for the regulatable transverse motionof the needle bar in zigzag sewing machines, in which lateral motion isimparted to the needle bar by a link non-detachably disposed between theneedle bar bearing and a driving lever oscillating about a fulcrum.

In known machines of this kind the end of the link articulated to theswinging driving lever is adjustable in a slot or the like of thedriving lever from the fulcrum in order to change the extent of thetransversal stroke of the needle bar, so that the removal of the end ofthe link from the fulcrum of the driving lever will result in anenlargement of the stitching width. When the end of the link is disposedin the fulcrum of the swinging driving lever, a transverse displacementof the needle bar does not take place and the machine is then adjustedfor the lock stitch.

This known drive arrangement suffers from the drawback that it ispractically impossible to provide for accurate adjustment of the.machine to lock stitch position. -Apart from the fact that the accuratefixing of the link in the fulcrum of the driving lever requires specialattention and care, the accuracy of adjustment is necessarily affectedby the unavoidable wear of the adjusting device which consists ofnumerous small parts. As a matter of experience, machines of this type,even if used only a relatively short time, will disclose a slighttendency of the needle bar to oscillate transversely when adjusted forthe lock stitch. For this reason, clean backstitching work cannot bedone for any length of time if the known driving arrangement for needlebars is employed.

It has been proposed already to eliminate completely the connectionbetween the link and the laterally swinging driving means during thesewing of the straight seam and to place the released 0 end of the linkon a. special bolt on the casing of the sewing machine. The knowndevices of this kind are, however, open to the objection that theconnecting screws between the link and the driving means have to beunscrewed in a bothersome manner and the lifted end of the link mustthen be placed on the stationary bolt of the casing of the machine andsecured thereto. Furthermore, such arrangements can be used only if boththe link and the swinging driving means are located outside the sewingmachine casing so as to be accessible. from the outside.

According to the invention, the drawbacks mentioned are eliminated bycausing the needle bar bearing or the link to become automaticallydisengaged from the laterally swinging driving means when the regulatingmember controlling the extent of motion of the needle bar is in zeroposition, and to remain-locked to the casing of the machine withoutrequiring complete disconnection of the link and the driving means. Forthis purpose, in the example shown in the drawing, thelink isarticulated to one end of the oscillatory driving lever so as to beimmovable on the latter, and the pivot of the oscillatory driving leveris formed by a special bolt displaceable and fixable in a slot of themachine casing and capable of varying its position on the lever relativeto the fulcrum for adjusting the extent of oscillation of the needlebar. This bolt engages with a pin thereof a longitudinal slot, which isopen at the joint of the link, of the oscillatory lever having a forkedtop end and being driven by a cam disc. When the pin at the fulcrum ispassed out of the slot of the oscillatory lever, it enters a groovearranged on the link vertically to the direction of sliding and thusprevents lateral displacement of the link by the driving lever freelyswinging about the link pin. Absolutely exact adjustment of the machineto the lock stitch position is therefore insured without effort andwithout special attention and loss of time.

The same effect can be attained also by other means, and the inventionis not limited to the arrangement described below but resides in theautomatic abolishment of the effective connection of the oscillatorydrive with the needle bar and in the automatic simultaneous locking ofthe needle bar bearing or link during displacement of the adjustingmembers for the extent of oscillation of the needle bar into zeroposition, i. e. when the machine is adjusted to lockstitching ortrimming.

By way of example, the invention is illustrated in the accompanyingdrawing, in which Fig. 1 is a view, partly in section, of the drivingmeans,

Fig. 2 a top view thereof, partly in section,

Fig. 3 a vertical section on the line AB of Fig. 2, and

Fig. 4 is a view of part of the sewing machine casing with the adjustingdevice for the width of the stitches.

Referring to the drawing, the main shaft a drives by means of thehelical gears b or other suitable means a cam disc 0 which engages theforked end of the oscillatory lever d and imparts thereto areciprocating motion. To the other end of the lever d the link e isarticulated in a forked manner by means of the bolt screw 1. Theoscillatory lever d has a longitudinal slot g which is open at the jointor axis of the bolt 1 and extends there into a groove h of the link edisposed vertically to the direction of displacement. In the grooves g,h slides with a suitable pin the bolt 2', which by means of guide facesand a slide is can be displaced in a slot m of the machine casing n. Atension spring and knurled nut p serve for clamping the bolt 2' andslide it at the desired point in the slot m. The accurate adjustment ofthe bolt 1 is facilitated by a scale on the slot m and a mark on theslide is.

The link e guided in a bearing q is connected at its free end by asuitable recess with the needle bar casing r or the needle bar guide s,the recess being formed so that during axial displacement of the link ean arc-like oscillation of the needle bar 1? about an axis u is insuredwhich lies in the extension of the axis of a ring looper horizontallymoved in front of the needle bar.

To avoid interference with the oscillation of the lever d at thejointing point with the link e, suitable play is provided at the jointof the grooves g, h and the faces of the oscillatory lever d and link 6,which are opposite to one another here, are preferably outwardly roundedor chamfered.

What I claim, is:

1. A drive for the regulatable transverse motion of the needle bar inzigzag sewing machines, comprising a bearing for the needle bar, adriving lever having a displaceable fulcrum constructed as a bolt forvarying the range of motion of the needle bar, a link non-detachablydisposed between said bearing and driving lever for imparting lateralmotion to said needle bar and articulated to said driving lever, andmeans for automatically disengaging the bolt from said driving lever torender the latter inefiective and for locking the link and needle baragainst lateral motion when said bolt is displaced into zero position.

2. A drive according to claim 1, in which the bolt is displaceable andfixable in a slot in the sewing machine casing and fitted with a pinengaging a longitudinal slot of the driving lever, said latter slotbeing open at the joint, said bolt passing out of the latter slot duringadjustment of the machine for straight stitching and into a groove ofthe link disposed vertically to the direction of displacement thereof.

CURT W'ILHELM SCHWEIGER.

